How unconscious actions are suppressed

Scientists at Cardiff University and University College London (UCL) have discovered an area of the brain that helps to suppress unconscious actions.

Researchers in Cardiff’s School of Psychology and UCL’s Institute of Neurology found that the brain’s ‘supplementary motor regions’ play a key role in suppressing unconsciously-triggered actions which occur when we encounter familiar objects and situations. The research addresses a key question: how do we actively decide what to do and avoid simply being governed by habits triggered by familiar things or people around us?

Neuroscientists have known for some time that these parts of the brain are implicated in directing actions, but the team’s research, published in the latest edition of the journal Neuron, shows that these areas are also involved in overruling ‘motor plans’ – potential actions triggered in the brain by visual cues.

Neuroscientists can experience difficulties in establishing a clear link between an area of the brain and a specific function. One way forward is to measure the consequences of damage to that region, however, lesions such as strokes are often large and span several different areas, making it difficult to convincingly display a link.

The team studied two extremely rare patients who had suffered small strokes located in the supplementary motor regions of the brain’s frontal lobes giving the team an unrivalled opportunity to examine the implications of damage to this specific area. These individuals showed deficits in their ability to voluntarily control movement.

Dr Petroc Sumner, School of Psychology said: “We are constantly encountering familiar people and objects which normally trigger action plans in the brain unconsciously. This activation can be very quickly suppressed again, presumably so that we are not forever making actions triggered by what we happen to see. This all happens ‘behind the scenes’ without our conscious knowledge. In the patients we studied, however, we found no suppression. We believe automatic triggers and how they are suppressed are critical to understanding how we overcome habits, and make choices between alternative actions.”

The findings are relevant to neurological disorders such as alien limb syndrome, where a person’s arm seems to take on a mind of its own, grasping any objects that come within reach, against the individual’s will. Patients who have suffered very extensive medial frontal damage, including the supplementary motor regions, can develop this disorder. These brain regions have also been implicated in the motor deficits experienced by patients with Parkinson’s disease.

Professor Masud Husain, UCL Institute of Neurology and Institute of Cognitive Neuroscience, said: “This research strongly indicates that part of the voluntary control of our actions actually involves overruling automatically activated motor plans.”

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